1. Field of the Invention
The present invention relates to a manufacturing method for a thin film magnetic head that is used in, for example, magnetic disk devices and recording/playback devices in computers and wordprocessors, in particular, to a manufacturing method for a thin film magnetic head that uses photolithographic technology to form the upper and lower magnetic poles by electroplating.
2. Background Information
Recently, because recording densities increase as the capacity of the magnetic disk recording devices increase, thin film magnetic heads have been widely applied. They are fabricated by using deposition technologies, such as electroplating and sputtering, and fine processing technologies based on photolithography. As shown in FIG. 3A, a conventional thin film magnetic head deposits an insulating film 2 on a substrate 1 of a ceramic material, forms the lower magnetic film 3 and the magnetic gap film 4 on top, and after depositing the conducting film 7 between the organic insulating films 5, 6, and the upper magnetic film 8 is formed and covered by a protective film 9. As shown in FIG. 3B, the front ends of the upper and lower magnetic films form the opposing upper and lower magnetic poles that have an intervening magnetic gap film 4, but the width of the upper magnetic pole 11 is narrower than that of the lower magnetic pole 10. Therefore, although the track width of the magnetic head widens based on the width of the lower magnetic pole 10, since the readout output decreases because it is set by the width of the upper magnetic pole, the problems were the difficulty in producing narrower tracks, and not adequately improving the performance and providing higher recording density in the thin film magnetic heads. Also, the projection of the lower magnetic pole has a skin that generates crosstalk that reaches the information recorded on neighboring tracks. Furthermore, since the upper magnetic film is formed using a photoresist on a higher level difference formed by the insulating layer and the conductive coil deposited on the lower magnetic film, it is difficult to control with high precision the track width of the upper magnetic pole.
Japanese patent number 63-55711 proposes a thin film magnetic head in which the upper and lower magnetic pole widths are matched by removing the projection of the lower magnetic pole by ion milling and using the upper magnetic pole or the resist layer formed on it as the mask, and narrower tracks are obtained without lowering the playback output. Similarly, the publication of unexamined Japanese patent application number 5-334621 and the publication of examined Japanese patent application number 6-101098 describe thin film magnetic head tracks where ion milling uses the upper magnetic pole as the mask to form an inclined surface from the magnetic gap side at the corners of the projection of the lower magnetic pole, and the track width only on the inclined surface is narrowed to match the widths of the upper and lower magnetic poles.
Furthermore, the manufacturing method for a thin film head disclosed in the publication of examined Japanese patent application number 5-74127 forms the protective film with a small milling rate on the lower magnetic pole, polishes the protective film to expose the lower magnetic pole, simultaneously ion mills to form the tapered concavity on the lower magnetic pole, and forms the upper magnetic pole on the gap layer in the concavity. Therefore, the track width is narrowed only in the inclined part of the upper magnetic pole to match the widths of the upper and lower magnetic poles.
However, the conventional thin film magnetic head described in Japanese patent number 63-55711 could solve the problems caused by the difference in track widths between the upper and lower magnetic poles and the crosstalk. However, the effect of the large level difference that is formed on the lower magnetic film could not be adequately eliminated by track width control. The ion milling speed is not uniform depending on the position, for example, it becomes slow near the side walls of the upper magnetic pole. In addition, since the lower magnetic pole material removed by ion milling is deposited again on the upper magnetic pole side, the problem is the difficulty in controlling the track width with high precision.
To realize a higher recording density, in addition to a narrower track, the film thicknesses, that is, the pole lengths, of the magnetic poles must be thinner. Since the conventional technology disclosed in the publication of examined Japanese patent application number 5-74127 generally has the problems of controlling with high precision the amount of polishing of the protective film and lower magnetic pole, the film thickness of the lower magnetic pole is hard to adequately control by only ion milling after polishing; this creates large fluctuations. Therefore, the problem is the inability to ensure sufficient reliability.
The manufacturing method for a thin film magnetic head of the present invention considered the conventional problems described above. The objective is to propose a manufacturing method for a thin film magnetic head that has high reliability and improved performance for a thin film magnetic head that has a pair of opposing magnetic poles with an intervening magnetic gap on the substrate that can match the track widths of both magnetic poles, precisely control the widths, and precisely control the film thicknesses of the magnetic poles to produce narrower tracks and a higher recording density.